"Isn't that dumb?" utters Penny in the first scene in this week's episode. Which kind of describes the premise for 'The Empathy Opitimization'.

After nine seasons, we know full well that Sheldon is a bit of a heartless git. But we love him because he can't help it. In recent years he's grown to become much more warm and understanding and knows exactly when to give people a warm beverage when they're upset. However, this week The Big Bang Theory did its notorious routine of throwing out all character development for the sake of a single plot and a few giggles.

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We've seen Sheldon ill on several occasions, and usually it just takes a few chest rubs and a verse of 'Soft Kitty' and he's back. For some reason this time it was too much to bear and he treated everyone like crap. And in a way that was much worse than usual, if you can believe that. Maybe it's because Amy is STILL away (we'll get on that in a minute).

That may well be the case as it took a brief conversation via Skype with Amy to make him realize how douchey he's been to his friends, and he goes on a bit of a Scrooge binge to make things right. Though, technically even this is insincere in the long run as it's only to make sure he gets a place on their Vegas party bus.

Generally, the episode was funny enough and Jim Parsons was on top form as a grumpy then well-meaning Sheldon. It just seemed a bit silly after everything that's come before and felt like this could have happened in season three, not nine.

One interesting development this week, however, was Raj and Emily's fallout. Yeah, remember Emily? You'd be forgiven if you forgot her. Raj's girlfriend is actually supposed to be a regular character but she only pops up every couple of months for some reason. And it's not like she's a hilarious character, either. It's as if she wondered in from the wrong CBS show, NCIS or something.

Now that we've seen another argument between the couple, hopefully this will mean one of two things; regular appearances from her or at least the end of their relationship farce by the season's finale.

And what's happened to Amy? Ever since she and Sheldon finally lost their virginities, she's appeared like Krang on a computer screen. It's probably down to Maiyim Bialik's availability (is she pregnant?), but if not, it's a bit random and disappointing. Fingers crossed she's back next week so the momentum of their relationship doesn't slow down too much.

The Big Bang Theory is in a dodgy place as it nears the end of its ninth season. After hundreds of episodes, there are only so many places you can take characters,and we've seen this journey of self-discovery with Sheldon many times now. We hope that he's learnt a bit more about being a normal human and he won't need to go through it again, but let's face it - he probably will.

Sheldon's Bazinga of the Week: "I've been on a trip myself recently. Not to Sin City but to Sincere City. Instead of genital warts the only growth you'll come back with is personal growth."